1. Field of the Invention
The present invention relates to a manufacturing method of a three-dimensional structure.
2. Description of the Related Art
Recently, there is a demand for easy and precise manufacture of a three-dimensional structure in a micro electro mechanical system (“MEMS”) structure and a sub-wavelength structure (“SWS”). A method of using a sacrifice layer (U.S. Pat. No. 4,662,746) and a wafer fusing method are known as conventional three-dimensional structure manufacturing methods.
The method of using the sacrifice layer coats and hardens a sacrifice layer after a first structure having a relief pattern is formed on a substrate. The sacrifice layer is filled in a concave part of the first structure, and is applied so as to cover the surface of the convex part of the first structure. Next follows polishing, such as chemical mechanical polishing (“CMP”) so as to expose the surface of the first structure. Next, a second structure is layered on the first structure in which the concave part is filled with the sacrifice layer, and the sacrifice layer is removed by a dry process. Thereby, a three-dimensional structure in which the first structure and the second structure are sequentially formed on the substrate.
The wafer fusing method prepares two first structures each having a relief pattern on a substrate or a first structure formed on a substrate and a second structure formed on a substrate. Next, this method hydrophilic-processes, superposes, and heats surfaces of concave parts of these two structures so as to fuse the patterns, and next finally removes the substrate on one side. Thereby, a three-dimensional structure can be obtained as in the method of using the sacrifice layer.
However, the polishing step in the method of U.S. Pat. No. 4,662,746 increases the number of steps and thus the cost. In addition, a polishing amount is different between a top of the concave part and a top of the convex part of the first structure, and thus the in-plane uniformity deteriorates and the yield may lower. Moreover, the three-dimensional structure manufacturing method using the wafer fusing method requires highly precise positioning, needs a long time to remove the substrate on one side, and causes a low productivity because processing of a large area is difficult.